Size effects on the magnetic behavior of γ-Fe2O3 core/SiO2 shell nanoparticle assemblies

The effect of core size on the magnetic behavior of nanoparticle assemblies of gamma-Fe2O3 core/SiO2 shell morphology is investigated. Long-range magnetostatic interactions are probed in two highly monodispersed experimental test systems of spherical nanoparticles with core diameters of 10 nm and 12.5 nm, and a shell thickness varying from 0 nm (bare particles) to similar to 50 nm. Zero-Field-Cooled magnetization curves are calculated by employing the Monte Carlo simulation technique in a mesoscopic-scale model for the assembly, assuming spin collinearity and coherent spin-reversal mechanisms. Simulation results reproduce the trend in the behavior of the Zero-Field-Cooled magnetization versus T curves in good qualitative agreement with the experimental findings. They also demonstrate that the increase of the magnetic core size results in a shift of the maximum magnetization peak, T-max, to higher temperatures due to enhanced dipolar coupling. The results shed light on how interparticle distance and magnetic core size influence the value of T-max through collective behavior and its transition to a single-particle superparamagnetic blocking temperature, T-B, as the assembly becomes magnetically diluted with increasing shell thickness.

Automated summary

The effect of core size on the magnetic behavior of nanoparticle assemblies was investigated, showing that an increase in magnetic core size results in a shift of the maximum magnetization peak to higher temperatures. The study sheds light on how interparticle distance and magnetic core size influence the behavior of the assembly.